The present invention relates to a dual pipe and a heat exchanger having the same, and more particularly, to a dual pipe and a heat exchanger having the same that can improve heat exchange efficiency of a heat exchanger by providing a dual pipe structure having an excellent performance in thermal conductivity.
An air conditioning apparatus for a vehicle is installed at the vehicle to air condition the interior of the vehicle by ventilating cold wind to the interior of the vehicle.
A general air conditioning system of such an air-conditioning apparatus performs a refrigeration cycle formed by connecting a compressor for compressing and transmitting a refrigerant, a condenser for condensing a refrigerant of a high pressure transmitted from the compressor, an expansion valve for decompressing a liquefied refrigerant by being condensed at the condenser, and an evaporator for cooling air ejected to the interior with an endothermic reaction by an evaporative latent heat of the refrigerant by evaporating the liquid refrigerant by heat exchange of the liquid refrigerant of a low pressure decompressed by the expansion valve with air ventilated to the interior side of the vehicle to a refrigerant pipe and air-conditions the interior of the vehicle through a refrigerant circulation cycle.
In order to enhance an air conditioning performance of the air-conditioning apparatus, a liquid refrigerant of a high temperature and a high pressure expanded by the expansion valve is supercooled, and as an apparatus that can appropriately adjust a superheat degree of a refrigerant exhausted from the evaporator is necessary, and thus a recently developed cooling system installs and uses a predetermined internal heat exchanger at the expansion valve inhalation side and the compressor inhalation side. Such an internal heat exchanger has a dual pipe structure formed with an inner pipe between a compression pipe in the evaporator and connected an outer pipe connected between the condenser and the expansion valve.
At the inner pipe, a refrigerant of a gas state of a low temperature and a low pressure flows, and at the outer pipe, a refrigerant of a liquid state of a high temperature and a high pressure flows, and the refrigerants flow in an opposite direction and exchange a heat. That is, by exchanging a heat of a liquid refrigerant of a high temperature and a high pressure injected into the expansion valve and a gap refrigerant of a low temperature and a low pressure exhausted from the evaporator, a temperature can be appropriately adjusted.
When such an internal heat exchanger has a large heat transfer rate, the internal heat exchanger has good heat exchange efficiency and thus the heat transfer rate greatly depends on a structure of the dual pipe. Further, in EU, in order to limit a greenhouse gas from releasing to air, a hydro-fluoro-carbon (HFC)-based 134a (R134a) refrigerant, which is a presently using global warming material will be replaced with a hydro-fluoro-olefin (HFO)-based 1234yf refrigerant, which is a low warming material, and a performance of a 1234yf refrigerant to be replaced in the future is deteriorated by about 15%, compared with a present refrigerant, i.e., R134a in an existing heat exchanger.
In order to improve an insufficient refrigerant performance, an air-conditioning apparatus such as a compressor, evaporator, and condenser should be improved and for this, much economic burdens occur.
Therefore, in order to improve efficiency and performance of an air-conditioner system for a vehicle according to a refrigerant change, a method of improving performance deterioration of a heat exchanger is requested.